Hi, I'm trying to get some help with my circuit. I've had people tell me that they won't help me because my project is dangerous. I would like to say that my safety is my own responsibility and any advice will not make this project more dangerous or put me in danger.
I've been having some problems firing my SCRs. I had two Teccor/Littelfuse S8040R SCRs (in parallel) hooked up to a capacitor charged to about 400v. The load (a coil) is connected to the + side of the capacitor, and the other end of the coil is connected to the anode of the SCR. The SCR cathode is connected to the capacitor minus. The gate is connected to a pushbutton switch in series with a 2.4v (two NimH AA's in series) supply, and the - of this is connected to the cathode. It would not fire when I pressed the button. I then disconnected the capacitor and measured the voltage between the gate and the cathode when the button was pressed, and it was only 1.44 volts! The SCR gates draw a lot of current which drags the battery voltage down a lot. When I hooked it up to my variable supply, the SCRs drew 3v, 3a! This makes sense to me because the SCR gate is supposed to be a diode, but then it is rated for 1.5v 30ma gate.
I then measured the resistance between the tab and anode pin of the SCR, and they're supposed to be connected, but overloaded my multimeter...
And the resistance between the SCR gates and cathodes is 82 ohms measured either way, and the diode voltage drop is around .1 volts, either way...
I'm very confused. Why won't the SCR fire? Why does the gate draw so much current? And why aren't the tab and anode pins connected? Thanks in advance, for any assistance at all.
I've been having some problems firing my SCRs. I had two Teccor/Littelfuse S8040R SCRs (in parallel) hooked up to a capacitor charged to about 400v. The load (a coil) is connected to the + side of the capacitor, and the other end of the coil is connected to the anode of the SCR. The SCR cathode is connected to the capacitor minus. The gate is connected to a pushbutton switch in series with a 2.4v (two NimH AA's in series) supply, and the - of this is connected to the cathode. It would not fire when I pressed the button. I then disconnected the capacitor and measured the voltage between the gate and the cathode when the button was pressed, and it was only 1.44 volts! The SCR gates draw a lot of current which drags the battery voltage down a lot. When I hooked it up to my variable supply, the SCRs drew 3v, 3a! This makes sense to me because the SCR gate is supposed to be a diode, but then it is rated for 1.5v 30ma gate.
I then measured the resistance between the tab and anode pin of the SCR, and they're supposed to be connected, but overloaded my multimeter...
And the resistance between the SCR gates and cathodes is 82 ohms measured either way, and the diode voltage drop is around .1 volts, either way...
I'm very confused. Why won't the SCR fire? Why does the gate draw so much current? And why aren't the tab and anode pins connected? Thanks in advance, for any assistance at all.